1. Field of the Invention
This invention relates to a transmitter for sensing a parameter to be measured and for converting the sensed parameter to an electrical signal representative of such parameter and, more particularly, to a transmitter with the capability of operating from a low voltage power supply and using a relatively small amount of power.
2. Prior Art
Transmitters known in the art sense a parameter and produce an output electrical signal representative of such parameter. Drive voltage of such transmitters has been a concern in the design of such transmitters, as start-up circuitry is difficult at low lift off voltages, but power consumption below the line zero value, for example 4 MA in a 4-20 MA transmitter has not been a significant factor in the design thereof. Such transmitters are often the two wire current transmitter design, where a power supply and series connected load is coupled through two wires to two terminals of such transmitter. A D.C. current which typically is 4-20 MA (milliamperes) is then controlled by the transmitter. Typically 4 MA is consumed by the transmitter electronics.